Tropical cyclone (TC) observations are used to examine changes in the TC climatology of the Australian region. The ability to investigate long-term changes in TC numbers improves when the El Niño-Southern Oscillation (ENSO) is considered. Removing variability in TC numbers associated with ENSO shows a significant decreasing trend in TC numbers at the 93–98% confidence level. Additionally, there is some indication of a temporal change in the relationship between ENSO and TC numbers, with ENSO accounting for about 35–50% of the variance in TC numbers during the first half of the study period, but only 10% during the second half.

The science actually predicted that global warming would make Australian tropical cyclones less common.

5.9.1 Tropical cyclonesSimilar to studies for other basins, Australian region studies indicate a likely increase in the proportion of the tropical cyclones in the more intense categories, but a possible decrease in the total number of cyclones.

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Since that time there has been a growing number of studies using results from medium and high resolution global climate models. The results from these studies indicate a consistent signal of fewer tropical cyclones globally in a warmer climate (Knutson et al 2006)